This invention relates to a method and apparatus for the treatment of tear-related disorders. More specifically, this invention relates to a method and apparatus which is used to treat cases of mild to moderate keratitis sicca or keratoconjunctivitis sicca (dry eye) conditions and contact lens wearing problems as well as pathologically dilated or constricted punctae.
Dry eye describes a continuum of problems which range from discomfort, to decreased vision and pain, to blindness. Its causes are aging, disease inflammatory processes and prescription drug side effects. A common condition is an inability to maintain a stable preocular tear film (PTF).
A film of tears, spread by the upper eyelid over the corneal and conjunctival epithelia, makes the surface of the eye smooth and optically clear. The tear film is composed of three thin layers which coat the surface of the eye. An outermost layer, an oily layer, is produced by small glands called meibomian glands at the edge of the eyelid. This outermost layer provides a smooth tear surface and reduces evaporation of tears. A middle watery layer is produced by the large lacrimal gland and a plurality of small glands scattered throughout the conjunctiva. This watery layer produces the largest amount of fluid and cleanses the eye by washing away foreign particles and irritants. An innermost layer consists of mucus produced by goblet cells in the conjunctiva. This inner layer allows the watery layer to spread evenly over the surface of the eye and helps the eye to remain wet. The mucus produced by this innermost layer adheres tears to the eye.
Normally the PTF is formed by a cooperative interaction of products from the meibomian glands, the lacrimal glands, and goblet cells; however, dry eye results when these glands produce less than an adequate amount of tears.
The treatment of dry eye is a common phenomenon. Tear deficiencies cause chronic irritation of the anterior segment, resulting in complaints of sandy, itching eye, conjunctivitis, metabolic disturbances of the cornea, and in extreme cases, a loss of visual function. Patients often present complaints and problems associated with a partial decrease in aqueous tear production. One cause of such complaints is partial atrophy of the lacrimal glands which is seen often in an aged patient and in some patients following infection. Atrophy can also occur in a younger patient wearing high water-content contact lenses, because of the increased requirement of the anterior segment for aqueous tears.
Thermal occlusion of the punctae opening and/or the proximal canaliculus has been employed in the treatment of dry eye conditions in the past. Initially performed with cautery or diathermy, permanent occlusion is now performed with the aid of medical grade lasers. When PTF loss into the naso-lacrimal trap is blocked, the volume of the remaining tears provide enhanced wetness of the anterior segment.
Epiphora and occasionally infections are two disadvantages of permanent occlusion. Also, there is a destruction of normal tissue which requires surgical intervention to reverse.
In order to avoid one or more of the foregoing disadvantages, alternative methods of temporary occlusion of a punctal opening have been developed. Such methods include temporary occlusion of the canaliculus by the insertion of small rods made from gelatin or collagen, or the use of temporary plugs made from bone cement. The blocking action of these agents is often either too brief or otherwise unsatisfactory.
As an alternative, patients with minor tear deficiencies were forced to use chronic multiple daily treatments with eye drops or cellulose inserts. Those with contact lens problems occasion decreased daily wear times or abandoned lens wear entirely.
The foregoing noted problems of mild to moderate dry eye were advantageously addressed by the introduction of a punctum plug as disclosed and claimed in the previously identified Freeman U.S. Pat. No. 3,949,750. The disclosure of this patent, of common assignment with the subject application, is incorporated herein by reference as though set forth at length.
Total occlusion of a lower punctum with a silicone plug of the Freeman design has proved beneficial in a number of patients suffering from moderate dry eye conditions.
Although reversible, this method of total occlusion is inappropriate for a very young person with very mild symptoms or with many problems associated with high water content contact lenses where it may be advantageous to diminish but not stop an outflow of lacrimal fluid.
The problems suggested in the preceding are not intended to be exhaustive, but rather are among many which may tend to reduce the effectiveness of prior methods and apparatus for modulating the flow of lacrimal fluid through a punctum and associated canaliculus. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that methods and apparatus for treating the moderate loss of PTF appearing in the past will admit to worthwhile improvement.